Flow monitoring apparatus

ABSTRACT

A method and portable apparatus for continually monitoring the flow of fluid in an open channel such as in a conduit having a known diameter, a known slope and of material having known surface characteristics. The liquid depth within the pipe is determined by means of an elongated hollow probe placed axially in the bottom of a channel containing the liquid and forcing gas under pressure there through. The measurement of the back pressure represents the depth of the liquid and enables the rapid determination of the rate of flow. It is contemplated that the portable apparatus be interconnected with a portable continual recorder such that the flow may be monitored over any given, desired, time period.

This is a continuation, of application Ser. No. 503,392 filed Sept. 5,1974, now U.S. Pat. No. 3,965,740.

BACKGROUND OF THE INVENTION

Whereas it has always been important to design a fluid flow system toaccommodate the maximum demand. This has been fairly regularlyaccomplished when a stable demand has been predicted. In the past rawsewage has been combined with natural drainage and the drainage systemhas included drain pipes larger than the predicted normal flow toaccommodate all flows at all times so it would not back up under timesof unexpected demand. With the increased interest and concern for theenvironment and health of our expanding population it is important tochannel raw sewage into one sewer system for proper treatment prior todischarge and the natural drainage or storm sewage and ground water intoanother system, which, because of its lack of contaminants may bedischarged with little or no preliminary treatment. For reasons ofefficiency, as well as best usage of treatment facilities, it isimperative that the system for handling raw sewage handle nothing morethan raw sewage. The raw sewage will be fed into raw sewage treatmentplants without overloading the facility and the environmental dangereliminated. It is for this reason that those systems which handle rawsewage must be monitored to predict any unpredicted increase in demanddue to storm inflow or ground water infiltration. The monitoring of theflow further enables an observer to quickly recognize an increase and/ordecrease caused by a failure of the sewage system which admits groundwater infiltration or surface drainage into the system or alternativelyreleases raw sewage to the surrounding environment.

With the need for a monitoring program employing portable, continuouslyrecording equipment in mind it has been suggested, and in many casesactively pursued, that the fluid flow within existing raw sewage systemsbe monitored either on a continual basis or intermittently over a periodof time such that infiltration, inflow and the increase and/or decreasein demand be readily predicted and accommodated.

A means for determining the flow within an open conduit is through theuse of the Manning flow relationship wherein if the pipe size is known,the slope of the pipe or conduit, and the material of the conduit aswell as the recorded depth, then using the Manning formula the flow canbe determined. One method of recording the depth in the past has beenthrough the use of a "Manning dipper" which essentially is a plumb boblowered through a manhole entry to the sewer liquid flow surface. Itwould record the depth of the liquid in the manhole and thus the flowcould be approximately be determined. One of the disadvantages of theManning dipper lies in the fact that it, as noted above, normally isdropped down a manhole which is normally an area of disturbed flow. Theliquid flows out of a conduit into the manhole base, which is notcoincident with the internal surface of the conduit and thusdisturbances are generated effectively changing the depth at that pointfrom what is actually is in the pipe where properties are known.Further, the Manning dipper, when used in a sewer, which transports rawsewage often becomes contaminated and the measurement is thus distortedby the interaction or hang-up of the various particles and materialcarried by the fluid within the sewer. These interference items causethe approximate pipe depth reading to be even less accurate.

With the above noted disadvantages of the present flow measuringtechniques in mind it is an object of the present invention to provide aportable means whereby the flow within an existing regular open channelconduit may be readily and reasonably accurately determined withoutgreat costs and further, with far greater accuracy than heretoforepossible.

It is another object of the present invention to provide a methodwhereby the depth within an open channel may be continuously recordedwithout requiring full time operator surveillance.

Further it is an object of the present invention to provide a novelapparatus for readily measuring the depth of flow in an open channelthus enabling the rate of flow within the channel to be accuratelydetermined.

It is a further object of the present invention to provide an apparatuswhich consists of a hollow probe which extends linearly into the channela sufficient distance to avoid disturbances within the manhole and ameans for placing and securing that probe accurately such that the depthof flow may be consistently determined without continual surveillance.

It is yet another object of the present invention to provide anapparatus which includes a recording device, a source of gas underpressure and an elongated hollow probe with an orifice in the outermostend such that the gas forced through the outermost end will bubblethrough the flowing liquid in the open channel. The resistance to theoutward flow of the gas can be recorded and thus determine the depth ofliquid over the probe and thereby, by use of the Manning formula, therate of flow of the liquid within the channel.

It is still another object of the present invention to provide aportable means to determine the rate of flow within an open channelwherein the apparatus for determining said flow is located very near thewall of the channel and therefore at a position of theoretical zerovelocity, greatly decreasing the possibility of interference with theflow or interference of the measurement by solid particles within theliquid flow.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an environmental view disclosing the flow measuring apparatuswherein the recorder and the air supply tank are located within themanhole of a sewer system and the supporting collar and the probe itselfare located within the conduit which carries the flow of liquid.

FIG. 2 is a partially schematic view emphasizing the location of theprobe and the probe supporting collar and their interconnection with theair supply tank and the flow meter, however, with the air supply tankand flow meter displaced for clarity.

FIG. 3 is an elevational view of the collar and probe showing how thecollar and probe will be displaced in the event there is substantialsludge in the bottom of the channel and further depicting how the collarwill be locked into position within the channel.

DETAILED DESCRIPTION OF DRAWINGS

As seen in FIG. 1, the preferred embodiment and use of the presentinvention is in a sewage flow line as schematically shown which hashollow cylindrical flow pipes 2 periodically interspersed with manholes4 having manhole openings 6 and ladders or the like 8 leading to thelower portions of the manhole. The manhole opening and ladder permitinspection of the system and placement of the flow meter within thesewer pipe as shown. As can be seen in this view, the liquid flowingwithin the sewer pipe, when it reaches the intersection with themanhole, will be caused to change to an uneven or disturbed flow whichwill greatly affect any depth measurements taken within the channelbottom of manhole 4.

The present invention which is a complete portable measuring andrecording package includes a recording device 10 which is anoff-the-shelf or standard item and therefore will not be described ingreat detail, but it is understood that it must be capable of recordinga differential in pressure as to be explained hereinafter. The recorder10 and the portable supply of pressurized air 12 in the form of a tankhaving a flow regulator 14 mounted thereon are shown as mounted uponshelf 16 within the manhole but could equally well be secured to theladder 8 or otherwise placed within the manhole. It is only requiredthat their location is relatively secure and above the normal expectedflow within the sewer and yet in the interest of compactness of theentire package, reasonably accessible.

The interconnection between the pressurized bottle 12 and the recorder10 is by way of a conduit 18 leading to a T-connection 20 havingextending outwardly therefrom a conduit 22 leading back to the recorder10 as well as the hollow conduit 24 which is semi-rigid and extendsdownwardly following the contour of the pipe and as explainedhereinafter, extends linearly upstream into the interior of the sewerpipe to be directly effected by the pressure created by the depth ofliquid flowing over the outer end thereof.

As can be seen in this view the probe 26 is a long, thin, hollow tubeextending linearly into the channel, lying in the cradle thereof andhaving a through bore 28 extending transversely there through and havingthe end of the tube closed. The tube is placed in the cradle such thatthe bore 28 lies in a horizontal plane. When the probe 26 is thus placedit has two openings to the liquid at the same depth allowing areasonably accurate approximation of the depth of the liquid even if oneof the holes should become plugged or the flow of gas otherwise impeded.Having two openings directly opposite each other permits a balancing ofthe pressures and therefore results in a more accurate reading whenmeasuring fluid such as sewage having large particles therein. The probelies in the cradle of the pipe and extends from a position upstream ofthe manhole where the gas releasing ports are located to a positionadjacent the manhole opening at which point it forms an approximatesemi-circle. The curved portion 29 is interconnected at its upper endwith the semi-rigid conduit 24 as described above. The semi-circularportion 29 lies inside a collar 30 and is contiguous therewith. Thecollar 30 has sufficient width to assure alignment with the conduit suchthat the probe 26 is parallel to the bottom of the conduit 2 and isexpandable by means explained hereinafter such that the collar may befixedly secured within the conduit 2.

Referring now to FIG. 2, it can be seen that the collar 30 is intimatelyengaged with the interior surface 32 of the conduit 2 and thus is at aposition of theoretical zero velocity preventing interference and/orhang-up with the solids or semi-solids within the flow. The probe 26extends longitudinally into the conduit 2 and lies within the cradlethereof and therefore is very close to the bottom of the conduit andalso in a position of theoretical zero velocity. The semi-circularportion 29 of the probe is secured adjacent the interior of the collar30 and does not vary therefrom until the upper portion thereof, aposition which is normally outside the expected flow. As can be seen thesemi-rigid conduit portion 24 extends into a T-connection 20 and thusinto a conduit 18 leading to a pressurized tank 12 as well as into aconduit 22 leading into a recorder 10 having a needle 3A or some othermeans of recording the back pressure generated by attempting to forcethe pressurized gas within the tank 12 through the probe 26 and itsassociated horizontal openings 28.

Referring now to FIG. 3, the means for locking the collar 30 in positionwithin the conduit 2 may more readily be seen. As seen in this figure,the collar is not a complete circle and has secured to its outer endsradially outwardly extending handle means 36 which terminates in axiallydirected handle portions 38.

As best seen in FIG. 2, the collar includes a plate 40 secured to theradial portion of each of the handles 36 and has extending there throughas seen in FIG. 3 a threaded bolt 42 having nuts 44 adjacent each of thebrackets 40. When it is desired to place the collar and attached probewithin the conduit 2, the collar may be compressed to a smallerdiameter, slipped into position and then allowed to expand. The collaris locked in place by means of the interior nuts 44. Further as seen inFIG. 3 the semi-spherical portions 29 of the conduit is closely marriedto the collar 30 thus possessing minimal impedance and lies in theposition of theoretical zero velocity.

FIG. 3, besides showing the details of the collar, and its lockingmechanism further discloses the means for approximating the depth of thefluid in a conduit 2 wherein a significant amount of sludge 50 hascollected at the bottom. In conditions such as this, the probe 26 isplaced at approximately the upper surface of the sludge 50 and thus thedepth between the sludge and the top of the flowing liquid is measured.Depending upon the depth of the sludge 50, the accuracy of thisinstallation will be determined, however, any changes in the flow willstill be readily determined by a change in the actual depth as measured.

Thus, as can be seen the present invention provides an efficient as wellas an inexpensive portable means for continually monitoring the flow ofliquid within an open channel. The amount of time that the monitoringsystem can be left to function and record any changes in depth will bedirectly dependent upon the amount of gas under pressure within thepressurized tank and the amount of time available for recording. Thepresent invention provides a unique approach and method to accuratelymonitor the flow in an open channel and because of the placement of thevarious devices does not restrict the flow within the channel and thusrenders an accurate measurement, a measurement which is accuratelyreflective of the flow which existed prior to the placement of themeasuring device.

What is claimed is:
 1. Portable flow-monitoring apparatus for use in acylindrical water or sewer pipe, comprising a flexible collar-likestructure adapted to fit within an open end of the pipe and contiguouswith the inside wall of the pipe, having the intended upper portion ofthe collar-like structure separated into a pair of ends adapted to bespaced farther apart or closer together to flex the collar-likestructure circumferentially, including means adjacent the respectiveends and adapted to expand the collar-like structure for frictionalretention in place against the inside wall of the pipe and, in contrast,to contract it for ready removal therefrom, sensor means mounted on partthereof and including a bubble outlet, and a bubble fluid conductorextending from outside the collar-like structure to the inside wallthereof and through about a semicircle in contact therewith and to thesensor means and bubble outlet.
 2. In apparatus for monitoring liquidflow under open-channel conditions through a cylindrical sewer or waterpipe or conduit wherein sensor means is located adjacent the invert orbed of the inside wall thereof, and including a bubble outlet, theimprovement comprising a conductor for bubble fluid from the exterior toan interior location adjacent such bed, the conductor extending from theexterior to the interior along an upper portion of the pipe or conduitand then in a circumferential direction downward, confined closelyadjacent such inside wall throughout its interior extent to such bed,thereby minimizing interference with such liquid flow, the apparatusincluding also means for applying lateral friction against such insidewall to aid in retaining such sensor means and bubble conductor inplace, wherein the means fo applying lateral friction includes anexpansible collar attached to the sensor means and bubble fluidconductor.
 3. Flow-monitoring apparatus according to claim 2, whereinthe bubble fluid conductor extends circumferentially along about halfthe inside perimeter of the expansible collar from its entrancethereinto from the exterior to its lowermost extend therein.
 4. Inapparatus for monitoring flow in an open conduit, the combination ofmounting means adapted to be secured within the conduit and only alongthe inside wall thereof to minimize flow disturbance and having a pairof ends adjacent one another but normally spaced apart, each endcarrying manually engageable means by which the ends may be positionedmore closely adjacent and also adjustment means by which the ends may bespaced further apart, and hollow pressure-sensing means adapted to besupported by the mounting means to extend from the exterior into theconduit only adjacent the inside wall thereof to minimize flowdisturbance and to terminate adjacent the flow bed.
 5. Flow-monitoringapparatus according to claim 4, wherein the means carried by the endsextend outwardly therefrom and thereby are precluded from entering theconduit.